[Fix]: Markers are too big in LineChart and ScatterChart

[singlayush]

Fix marker sizing in LineChart and ScatterChart

Problem

Markers in LineChart and ScatterChart were rendering too large compared to expected behavior (e.g., Plotly). The previous formula (markerSize * extraMaxPixels) / maxMarkerSize would essentially result in scaling markers based on the extraMaxPixels. But we would only want to scale down and not scale up. The scaling down is needed to ensure there is no overflow out of the chart, while scaling up serves no purpose and results in too big markers.

Solution

Updated the marker radius calculation to use conditional logic:

extraMaxPixels > maxMarkerSize 
  ? markerSize 
  : (markerSize * extraMaxPixels) / maxMarkerSize

Logic:

• If extraMaxPixels > maxMarkerSize: Use the actual markerSize directly (enough space available)
• Otherwise: Scale down proportionally to fit within available space

Test Run: https://github.com/microsoft/fluentui-charting-contrib/actions/runs/21618414015

Examples

markerSize	extraMaxPixels	maxMarkerSize	Result
100	10	100	10 (extra < max, scaled down significantly: 100 × 10 / 100)
2	100	2	2 (extra > max, use markerSize directly no scaling needed)
20	25	30	16.67 (extra < max, scaled down slightly: 20 × 25 / 30)

Changes

• LineChart.tsx: Updated all 4 marker radius calculations to use consistent formula
• ScatterChart.tsx: Updated marker radius calculation with same formula
• Z-order fix: Markers now render on top of lines (LineChart)

Screenshots

Before

### Plotly ### After ### Before ### Plotly ### After

Before

### Plotly

Plotly

### After

Before

### Plotly ### After

Testing

• Verified with single data point
• Verified with multiple data points (similar marker sizes)
• Verified with varying marker sizes
• Verified markers appear above lines

[github-actions]

📊 Bundle size report

Package & Exports	Baseline (minified/GZIP)	PR	Change
react-charts DeclarativeChart	756.061 kB 217.557 kB	756.132 kB 217.581 kB	71 B 24 B
react-charts LineChart	416.789 kB 126.304 kB	416.852 kB 126.327 kB	63 B 23 B
react-charts ScatterChart	396.616 kB 120.448 kB	396.622 kB 120.455 kB	6 B 7 B

Unchanged fixtures

Package & Exports	Size (minified/GZIP)
react-charts AreaChart	406.227 kB 124.399 kB
react-charts DonutChart	316.668 kB 94.327 kB
react-charts FunnelChart	308.221 kB 91.258 kB
react-charts GanttChart	389.336 kB 117.968 kB
react-charts GaugeChart	316.099 kB 93.739 kB
react-charts GroupedVerticalBarChart	397.214 kB 120.569 kB
react-charts HeatMapChart	391.417 kB 119.694 kB
react-charts HorizontalBarChart	296.395 kB 85.942 kB
react-charts HorizontalBarChartWithAxis	63 B 83 B
react-charts Legends	235.306 kB 69.271 kB
react-charts PolarChart	345.279 kB 105.359 kB
react-charts SankeyChart	213.881 kB 65.62 kB
react-charts Sparkline	91.393 kB 28.708 kB
react-charts VerticalBarChart	433.691 kB 126.054 kB
react-charts VerticalStackedBarChart	403.128 kB 121.411 kB

_{🤖 This report was generated against 72fa991316ec4a9d207a2926f4bf41c683314bad}

[github-actions]

Pull request demo site: URL

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[krkshitij]

The radius calculation can be extracted into a common function.

[krkshitij]

Removing the role and aria-label attributes will affect screen reader accessibility. In the new structure, these attributes can be set on individual groups of points.